U.S. patent number 4,039,956 [Application Number 05/610,538] was granted by the patent office on 1977-08-02 for electronic indicator.
This patent grant is currently assigned to General Motors Corporation. Invention is credited to Mark A. Franklin, Ronald W. Shimanek.
United States Patent |
4,039,956 |
Shimanek , et al. |
August 2, 1977 |
Electronic indicator
Abstract
An electronic frequency indicator for an AM/FM receiver
utilizing a plurality of light-emitting diodes. The intensity of
the diodes is varied to achieve greater resolution for the number
of diodes in the indicator.
Inventors: |
Shimanek; Ronald W. (Kokomo,
IN), Franklin; Mark A. (Kokomo, IN) |
Assignee: |
General Motors Corporation
(Detroit, MI)
|
Family
ID: |
24445422 |
Appl.
No.: |
05/610,538 |
Filed: |
September 5, 1975 |
Current U.S.
Class: |
455/157.2;
116/DIG.29; 116/241; 334/86; 345/39; 345/440.2; 324/96; 455/159.2;
324/76.72 |
Current CPC
Class: |
H03J
1/02 (20130101); Y10S 116/29 (20130101) |
Current International
Class: |
H03J
1/00 (20060101); H03J 1/02 (20060101); H03J
003/14 (); H04B 001/16 () |
Field of
Search: |
;325/455,398
;324/78J,78Q,122,96 ;334/36,37,86
;116/124.1R,124.4,DIG.29,DIG.30,DIG.31 ;340/324R,166EL |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
"Sensitive F-M Tuning Indicator" -- J. Skingley -- June 1974,
Wireless World, vol. 80, No. 1462, pp. 173-174..
|
Primary Examiner: Safourek; Benedict V.
Assistant Examiner: Bookbinder; Marc E.
Attorney, Agent or Firm: Duke; Albert F.
Claims
Having thus described our invention what we claim is:
1. An electronic indicator circuit comprising a plurality of
parallel connected light emitting diodes, a variable DC voltage
source, a source of regulated DC voltage, voltage divider means
connecting each of said diodes to said regulated source and
establishing a reference voltage at one terminal of each of said
diodes, transistor means connected in circuit with respective ones
of said diodes and responsive to the voltage established at said
terminal and to said variable DC voltage source for continuously
varying the current through each of said diodes over a range from a
minimum to a maximum level in sequence as said variable DC voltage
source is varied over a predetermined voltage range whereby each
diode is successively activated and previously energized diodes
remain activated.
2. An electronic frequency indicator for a radio frequency receiver
having a dial plate comprising a plurality of light emitting diodes
distributed across the dial plate at desired frequency increments,
means providing a variable DC voltage which varies with frequency,
a source of regulated DC voltage, voltage divider means connecting
each of said diodes to said regulated source and establishing a
different voltage at one terminal of each diode, first and second
transistor means of opposite conductivity type connected in circuit
with each of said diodes and responsive to the voltage established
at said terminal and to said variable DC voltage for varying the
current through each of said diodes from a minimum to a maximum and
back to a minimum level corresponding to a range of frequencies
whereby only one diode is activated at any time but successive
individual diodes are activated and previously activated diodes are
deactivated as the frequency is varied.
3. An electronic frequency indicator for a radio frequency receiver
having a dial plate comprising a plurality of light emitting diodes
distributed across the dial plate at desired frequency increments,
means providing a variable DC voltage which varies with frequency,
a source of regulated DC voltage, voltage divider means connecting
each of said diodes to said regulated source and establishing a
different voltage at one terminal at each diode, the voltage at the
diode located at successively higher frequencies being a higher
voltage, first and second transistors of opposite conductivity type
connected in shunt with each of said diodes and responsive to the
voltage established at said terminal and said variable DC voltage
for varying the current through each of said diodes from a minimum
to a maximum and back to a minimum level corresponding to a
frequency range from a lower frequency to a higher frequency,
voltage dropping means connected in circuit with each of said
second transistors whereby a plurality of light emitting diodes are
activated at any one time.
Description
This invention relates to solid state electronic indicator devices
and more particularly to an electronic dial indicator for AM and FM
receivers.
Prior art solid state indicator devices include a plurality of
light emitting diodes (LED) positioned on a circuit board located
behind a dial or scale of the device. The number of diodes required
depends on the scale gradations or the resolution desired. The LEDs
are usually successively energized to provide a bar graph or
thermometer-like display indicating the value of a monitored
variable.
In accordance with the present invention an improved solid state
indicator for a radio receiver is provided which utilizes an array
of LEDs in place of the conventional pointer for indicating the
frequency to which the receiver is tuned. In one embodiment of the
invention the LEDs are energized in a manner to permit a bar-type
display that moves across the tuning dial as the frequency is
changed. Succeeding individual LEDs gradually vary in brightness as
the frequency changes, reaching full brightness when the frequency
selected corresponds to the LED's position relative to the dial.
Previously energized LEDs maintain full brightness. In another
embodiment only one LED is energized at any given time and its
brightness is varied from a minimum to a maximum and then back to a
minimum as the frequency is varied over the range at which the LED
is positioned, such as for example, 2 MHz. As the frequency is
varied across the radio band, successive individual LEDs are
energized and the previously energized LED is deenergized. A third
embodiment combines features of the other two embodiments by
energizing a maximum of three LEDs at any one time. As the
frequency at which an LED is positioned is approached, the center
LED is brightest while the one preceding it grows dimmer and the
one succeeding it begins to grow brighter.
A more complete understanding of the present invention may be had
in the following detailed description which should be read in
conjunction with the drawings in which:
FIG. 1 is a front view of a radio dial plate and showing the
physical location of an array of light emitting diodes relative to
the dial plate;
FIG. 2 is a circuit diagram of a first embodiment of the
invention;
FIG. 2a is a waveform useful in illustrating the operation of the
embodiment shown in FIG. 2;
FIG. 3 is a circuit diagram of another embodiment of the
invention;
FIGS. 3a and 3b are waveforms showing two different modes of
operation of the circuitry shown in FIG. 3 depending on the
indicator width desired.
Referring now to the drawings and initially to FIG. 1, the numeral
10 generally designates the frequency indicator for an AM/FM
receiver. The indicator includes a cover 12 and a scale 14
containing a slot 16. A plurality of light emitting diodes D1-D11
are mounted on a circuit board, not shown, and positioned behind
the slot 16 extending over the FM band of 88 MHz. to 108 MHz. in 2
MHz. increments and over the AM band of 550 KHz. to 1600 KHz. in
approximately 100 KHz. increments.
Referring now to FIG. 2, circuitry for controlling the energization
of the LEDs D1-D11 in accordance with one embodiment of the
invention is shown. Only three of the eleven LEDs, namely, D1, D2
and D3 are shown in FIG. 2. The LED D1 is connected between B+ and
ground through a resistor 18 and On/Off switch 20. The value of the
resistor 18 is selected so that the LED D1 is energized to full
brilliance as long as the radio On/Off switch 20 is closed. The LED
D2 is connected between voltage divider resistors 22 and 24.
Similarly, LED D3 is interposed between voltage divider resistors
26 and 28. PNP transistor Q1.sub.2 has its emitter electrode
connected to a junction between the anode of LED D2 and resistor 22
and its collector connected to a junction between the cathode of
LED D2 and resistor 24. The base electrode of Q1.sub.2 is connected
through a current limiting resistor 30 to a variable voltage source
32. The source 32 may be the source usually provided for varying
the voltage across a varactor diode for controlling the tuning of
the receiver. With a mechanically tuned receiver the frequency of
the local oscillator may be converted directly to a linear tuning
voltage by means of a frequency-to-voltage converter which can be
used as the source 32. A transistor Q1.sub.3 has its emitter
connected to a junction between the anode of LED D3 and the
resistor 26 and its collector connected to a junction between the
cathode of LED D3 and the resistor 28. The base of transistor
Q1.sub.3 is connected with the source 32 through a current limiting
resistor 34. It will be understood that the remaining LEDs D4-D11
are connected to B+ in the same fashion as the LEDs D1-D3.
Typical values for the resistors shown in FIG. 2 are as follows:
Resistor 18=560 ohms, resistor 22=510 ohms, resistor 24=50 ohms,
resistor 26=460 ohms, and resistor 28=100 ohms. With a nominal B+
voltage of 8 volts a current of 10 milliamps flows through the LED
D1 to produce full brilliance. LEDs D1-D11 each drop approximately
21/2 volts. As the receiver is tuned over the AM or FM band the
output of the source 32 preferably varies from a voltage of 1.8
volts to 7.5 volts. Accordingly, when the radio is tuned to the low
end of the AM or FM band so that the output of the source 32 is 1.8
volts, the transistors Q1.sub.2, Q1.sub.3, etc., for each of the
LEDs D2-D11 will be forward biased to saturation. Consequently, as
shown in FIG. 2a, only the LED D1 will be energized and will be at
full brilliance. As the voltage of the source 32 is increased,
current flow through the transistor Q1.sub. 2 decreases and current
flow through the LED D2 increases as shown in FIG. 2a so that at
approximately 90 MHz. on the FM dial and 650 KHz. on the AM dial
both the LEDS D1 and D2 are at full brilliance. After the LED D2
reaches full brilliance a continuation of the increase of voltage
from the source 32 will cause current to diminish through the
transistor Q1.sub.3 and cause an increase of current through the
LED D3 until at approximately 92 MHz. on the FM dial and 750 KHz.
on the AM dial the LED D3 reaches full brilliance. Succeeding LEDs
will be energized from a minimum to a maximum brilliance while the
previous LEDs are maintained at full brilliance as the voltage of
the source 32 is increased until at a voltage of approximately 7.5
volts or at the upper end of the AM and FM band all of the LEDs
D1-D11 will be energized at full brilliance.
Referring now to FIG. 3 components which are identical with those
previously discussed in FIG. 2 are designated by identical
reference numerals. In FIG. 3, NPN transistors Q2.sub.1, Q2.sub.2,
and Q2.sub.3 have been added. Each of the NPN transistors has its
emitter-collector electrodes connected in parallel with the LEDS
D1, D2 and D3, respectively. The base of each of the NPN
transistors is connected with the source 32 through a string of
diodes collectively designated D.sub.w and individual current
limiting resistors 36, 38 and 40, respectively.
The operation of the circuit shown in FIG. 3 will be explained with
reference to FIGS. 3a and 3b. Referring first to FIG. 3a; with the
voltage source 32 at 1.8 volts the LED D1 is at full brilliance and
the transistors Q1.sub.2, Q1.sub.3 are in saturation so that no
current flows through the LEDS D2 and D3, the NPN transistors
Q2.sub.1, Q2.sub.2, Q2.sub.3 are cut off. As the voltage of the
source 32 increases, current flow through the PNP transistor
Q1.sub.2 will decrease and current flow through the LED D2 will
increase. Depending upon the number of diodes in the string
D.sub.w, at a particular voltage of the source 32 the transistor
Q2.sub.1 begins to conduct and shunt current from the LED D1.
Thereafter, as shown in FIG. 3a, the transistor Q1.sub.2 begins to
turn off and current flow through the LED D2 begins to increase.
After the LED D2 reaches full brilliance the transistor Q2.sub.2
begins to conduct and shunt current away from the LED D2.
Similarly, at some voltage after Q2.sub.2 begins conduction,
Q1.sub.3 begins to turn off and current flows through the LED D3.
After the LED D3 reaches full brilliance the transistor Q2.sub.3
begins to turn on and shunt current away from the LED D3.
Consequently, the LED D1 is varied from maximum brilliance to
minimum brilliance or no light output while the LEDs D2 and D3 are
varied from minimum or no light output to maximum and back to
minimum brilliance. It will be understood, of course, that the LED
D1 could also be varied in the same manner as the LEDs D2 and D3 if
such is desired.
By increasing the number of diodes in the diode string D.sub.w the
number of LEDs which are energized at any one time may be
increased. For example, as shown in FIG. 3b, all three of the LEDs
D1, D2 and D3 are at some intensity level between minimum and
maximum at a particular voltage or frequency. For example, at 90
MHz. the LEDs D1 and D3 are approximately one-quarter brilliance
while the LED D2 is at maximum brilliance. Thus, as the frequency
at which an LED is positioned is approached, that LED is brightest
while the brightness of the preceding LED diminishes and the
brightness of the succeeding LED increases.
It will be apparent from the above that we have provided an
improved electronic indicator which reduces the number of light
emitting diodes necessary to achieve a predetermined degree of
resolution by varying the intensity of the light emitted from the
diode over a predetermined range of the variable being
monitored.
* * * * *